Intravenous infusion is carried out for the purpose of supplying nutrients to maintain a patient's life when oral or nasal feeding is impossible or insufficient, when the digestion and absorption functions of the patient are in a poor state even if such a feeding means can be carried out, or when the passage of food through the digestive tract makes the patient's condition or disease more serious.
Examples of commercially available infusion preparations include a sugar infusion liquid which contains reducing sugars and the like, an amino acid infusion liquid which contains essential amino acids and the like, an electrolyte infusion liquid which contains electrolytes and the like, a fat emulsion which contains a plant oil emulsion and the like, and a vitamin mixture. These infusion preparations are appropriately selected depending on the condition of the patient and are mixed upon use.
However, mixing these preparations at the time of their use requires complex handling and, above all things, raises the problem of microbial contamination. With the aim of overcoming such problems, various infusion preparations in which some of the aforementioned ingredients are mixed in advance have been proposed. Infusion preparations which contain sugars, amino acids, electrolytes and fat emulsions, all being essential nutrients to be supplied, are especially useful from a clinical point of view.
However, since these sugar liquids, amino acid liquids, electrolyte liquids and fat emulsion are different from one another in terms of the conditions for their stable existence, various problems arise when they are mixed and the mixture becomes useless in many cases.
For example, because of its unstable nature, a fat emulsion is apt to form bulky fat particles and to cause phase separation (creaming) when mixed with other infusion liquids. In particular, divalent cations in an electrolyte infusion liquid cause aggregation and disintegration of fat emulsion particles.
In the case of an electrolyte infusion liquid, since it contains calcium and phosphoric acid as essential components to maintain the balance of electrolytes, it is apt to form calcium phosphate by the reaction of calcium with phosphoric acid and therefore to generate turbidity and precipitation. In order to prevent the formation of turbidity and precipitation, such an electrolyte infusion liquid is usually adjusted to a low pH value (less than pH 5). When such a electrolyte infusion liquid is mixed with an amino acid infusion liquid, the pH of the mixture increases to the amino acid pH value because of the strong buffer action of amino acids, thus requiring a large quantity of acidic materials (for example, hydrochloric acid, acetic acid and the like) to keep the pH value at a low level. However, acid materials can be used only in a limited amount because a large quantity of acid spoils the balance of the infusion components. As a consequence, the pH value of the mixture of electrolyte and amino acid infusion liquids cannot be lowered to a satisfactory level, thus resulting in the generation of turbidity and precipitation at the time of heat sterilization of the mixture.
In addition, when a mixture of an amino acid infusion liquid with a sugar infusion liquid is sterilized by heating, considerable coloring occurs due to the Maillard's reaction.
As described above, it is difficult to prepare a storable infusion preparation which contains a sugar, amino acids, electrolytes and a fat emulsion in advance, because mixing these different types of infusion liquids or emulsions causes various problems such as precipitation, phase separation, denaturation, coloring and the like. Because of these problems, a fat emulsion, a sugar infusion liquid, an amino acid infusion liquid and an electrolyte infusion liquid are ordinarily mixed upon use. As a consequence, an infusion preparation which contains a sugar, amino acids, electrolytes and a fat emulsion and can be stably stored has been desired.